Update on Mekong River Dolphins in Cambodia

An international team of scientists, including several from the CSG, spent the week of 9-13 January 2012 in Cambodia working with Cambodian counterparts on efforts to refine understanding of the status of dolphins in the Mekong River (Orcaella brevirostris), determine cause(s) of the exceptionally high calf mortality documented in recent years, and improve protection measures (especially pertaining to bycatch in gillnets). This was a follow-up to an earlier meeting in October 2009 (see previous report on this website under Special Projects: Mekong River Irrawaddy Dolphins).

A recent publication led by Gerry Ryan of the WWF-Cambodia dolphin project had estimated current abundance of this relict population as only 85 (95% CI= 77.9-91.2) based on a novel mark-resight estimation method (Ryan et al. 2011). Perhaps more importantly, Ryan and his co-authors estimated seniority at 0.999 (0.028 SE), recruitment at 0.001, and population growth rate at 0.978, concluding: “Although the population size appears to be stable, we believe this represents the slow disappearance of a long-lived animal with no recruitment.”

A key finding by the visiting scientific team (which included veterinarians Frances Gulland, Thijs Kuiken, Antonio Fernández, and Paul Jepson) was that there is no evidence to support the idea that a disease process is involved in the high incidence of calf deaths. Nor is there any support for the view that this population is suffering significantly from contaminant exposure or inbreeding. Entanglement in fishing gear, mainly gillnets, is unquestionably the primary cause of death for non-calves, but the primary cause(s) for the very high mortality of calves remain unknown.

By the end of a week of meetings, laboratory work, and field observations, the responsible parties in Cambodia – the Commission for Conservation and Development of Mekong River Dolphin Ecotourism Zone, the Fisheries Administration of the Ministry of Agriculture, Forestry and Fisheries, and WWF-Cambodia – signed a document called the Kratie Declaration on the Conservation of the Mekong River Irrawaddy Dolphins. The declaration commits them to work collaboratively and with a sense of urgency to address the conservation and scientific recommendations developed jointly by the international experts and the local and regional participants who attended the workshop.

The Kratie Declaration, together with its appendices which contain the findings and recommendations from the workshop, is available for download from the Downloads tab on this site or by following this link.